1) Field of the Invention
The present invention relates to a heat-resisting adhesive composition for electronic parts to be used for TAB tapes, adhesive tapes for fixing the leadframe or for adhering between parts around leadframes making up a semiconductor device, e.g., leadpins, semiconductor chip mounted substrates, heat spreader, semiconductor chips themselves, and to an adhesive tape for electronic parts using the above adhesive composition.
2) Description of the Related Art
Conventionally, adhesive tapes for fixing a leadframe, TAB tapes, etc., are used as adhesive tapes for use in the interior of resin-molded type semiconductor devices. For example, the adhesive tapes for fixing the leadframe have been used to fix lead pins of the leadframe in order to enhance the efficiency for producing the leadframe itself and the whole semiconductor assembly stages. In general, a leadframe manufacturer tapes a leadframe, and brings it to a semiconductor manufacturer, at which a semiconductor chip is mounted thereon followed by molding the leadframe with a resin. For this reason, it has been required for the adhesive tapes for fixing the leadframe not only to possess general reliability in a level required for semiconductor and enough processability at the time of taping, but also to possess sufficient adhesive strength at room temperature immediately after taping and heat resistance enough for withstanding thermal process at the stages of assembling semiconductor devices.
Conventionally, the adhesive tapes for use in such an application include adhesive tapes applying on a support film of a polyimide film, etc., an adhesive comprising polyacrylonitrile, polyacrylate or a synthetic rubber resin such as acrylonitrile-butadiene copolymer solely, or modified with any other resin or blended with any other resin to come into a B-stage. Both-sided adhesive tapes using thermoplastic polyimide resin having high reliability and high heat resistance have been utilized recently.
In recent years, resin-molded type semiconductor devices (semiconductor packages) as shown in FIGS. 1-3 have been developed and produced. In FIG. 1, the device has a construction in which lead pins 3 and a metal plane 2 are connected by means of an adhesive layer 6, a semiconductor chip 1 is mounted on the metal plane 2, and they are molded with a resin 5 together with bonding wires 4 between the semiconductor chip 1 and the lead pins 3. In FIG. 2, the device has a construction in which the lead pins 3 and the semiconductor chip 1 are connected by means of an adhesive layer 6 and they are molded with a resin 5. In FIG. 3, the device has a construction in which the semiconductor chip 1 is mounted on a die pad 7, electrodes 8 and the die pad are connected by means of the adhesive layers 6, the semiconductor chip 1 is electrically connected to the electrodes 8 and the electrodes 8 are electrically connected to the lead pins 3 by means of bonding wires 4, and they are molded with a resin 5. In these cases, in general, single-layer adhesive tapes or both-sided adhesive tapes are used for the adhesive layer 6. Further, the adhesive layer 6 may be produced directly on the leadframe or the semiconductor chip by printing or applying a liquid adhesive by means of a dispense.
In the adhesive layers in the resin-molded type semiconductor devices shown in FIGS. 1-3, the use of an adhesive tape to which a conventional adhesive is applied has the problems that the generated gas stains the lead to cause deterioration of the adhesive strength or causes generation of package crack, because of insufficient heat resistance. It is therefore required to develop adhesives for electronic parts having sufficient heat resistance and reliability and adhesive tapes for electronic parts using them.
In order to satisfy the above described requirements, various kinds of adhesive tapes using thermoplastic polyimide resin having excellent electric reliability, such as those of having 3-layered structure or single-layer structure. However, the thermoplastic polyimide resins have various drawbacks. Many of them have a high glass transition temperature (Tg) and require an adhesion temperature of 300.degree. C.-400.degree. C. or higher, by which they causes oxidation and strains of the leadframe or damaging the semiconductor chips.
On the other hand, when thermoplastic resins having a low Tg are used for allowing adhesion at a low temperature, there causes problems of reducing reliability of the package, because the resins flow in the assembling stages using heat and pressure, such as wire bonding stage, molding stage, IR reflowing stage etc. and, consequently, sufficient adhesion is impossible to carry out.
The present invention has been made for the purpose of solving such problems in the prior arts. Namely, an object of the present invention is to provide a heat-resisting adhesive composition for electronic parts capable of adhesion at a relatively low temperature and having sufficient reliability without causing flowing of the resin in stages using heat and pressure, and to provide an adhesive tape for electronic parts using the same.